(Sorry for being so tardy — 2018 has been a year of deadlines so far.)
Of course behaviour is not always situational. In the end it comes down to what fundamental choice we make when observing and approaching the world. Do we think people are by and large good, until proven otherwise, or do we suspect them all of being out to take advantage of us, until they’ve really, really earned our trust (and even then…)?
I don’t think there is a ‘right’ position. But the choice you make has consequences, and it’s worth reflecting on those.